An aqueous modified polyisocyanate of the self-emulsifiable type is obtained by reacting an isocyanate derivative such as an isocyanulate group-containing polyisocyanate with a nonionic modifying agent such as an alkoxy polyoxyalkylene glycol.
The aqueous modified polyisocyanate is required to be good in dispersion stability and stability of the isocyanate group in water.
An aqueous modified polyisocyanate poor in dispersion stability in water sediments after dispersed in water to fail to sufficiently develop the expected performance (coating film performance or adhesion performance), and turbidity caused by aggregates of this modified product arises in a coating film formed by a coating composed of an aqueous dispersion of the modified product, thereby markedly impairing the appearance thereof.
A modified polyisocyanate poor in stability of the isocyanate group in water cannot secure a sufficient pot life when it is used as a constituent component (hardener) of a coating or adhesive.
As aqueous modified polyisocyanates good in dispersion stability and stability of the isocyanate group in water, the present assignee has proposed:
a modified polyisocyanate of the self-emulsifiable type obtained by subjecting HDI to urethane modification with a dihydric alcohol having 4 to 35 carbon atoms, the total number of carbon atoms branched of which is 2 to 33, a hydrophilic surfactant (for example, methoxy polyoxyethylene glycol) having an active hydrogen group capable of reacting with an isocyanate group and 3 to 90 alkylene oxide units, an aliphatic compound (for example, methyl ricinoleate) having an active hydrogen group capable of reacting with the isocyanate group and 8 or more carbon atoms and a non-branched glycol having 1 to 10 carbon atoms, and to urethodionation and isocyanuration (see Patent Art. 1); and
a modified polyisocyanate of the self-emulsifiable type obtained by reacting an isocyanate derivative such as an HDI derivative with a hydrophilic surfactant (for example, methoxy polyoxyethylene glycol) having at least one active hydrogen group capable of reacting with an isocyanate group and a fatty acid ester (for example, methyl ricinoleate), in which the total number of carbon atoms in a fatty acid and a hydroxyl group-containing compound that become raw materials is 8 or more, and which has at least one active hydrogen group capable of reacting with the isocyanate group, at specific proportions (see Patent Art. 2).
The present assignee has also proposed, as an isocyanate group-containing adhesive having a high fixing rate to inorganic fibers, a modified polyisocyanate obtained by reacting an organic polyisocyanate with an ionic hydrophilic group-containing active hydrogen compound and a nonionic hydrophilic group-containing active hydrogen compound (see Patent Art. 3).    Patent Art. 1: Japanese Patent No. 2959399;    Patent Art. 2: Japanese Patent No. 3089623;    Patent Art. 3: Japanese Patent Application Laid-Open No. 2003-119449.